Goal creation with pending retries, calendar task links, session-goal linking

src/main/java/com/studysync/domain/entity/StudySession.java

@@ -1,6 +1,7 @@
 
 package com.studysync.domain.entity;
 
+import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.core.RowMapper;
 import org.slf4j.Logger;
@@ -42,7 +43,11 @@ public class StudySession {
     private String improvementNote;
     private int pointsEarned;
     private String sessionText;
-
+
+    /** Optional links to the goal/task this session works on. */
+    private String goalId;
+    private String taskId;
+
     // Real-time tracking fields
     private boolean isActive;
     private LocalDateTime lastUpdateTime;
@@ -121,21 +126,51 @@ public void save() {
             MERGE INTO study_sessions (id, date, start_time, end_time, duration_minutes, completed,
                                       focus_level, confidence_level, notes, subject, topic, location,
                                       outcome_expected, actual_work, what_helped, what_distracted,
-                                      improvement_note, points_earned, session_text, is_active,
-                                      last_update_time, current_elapsed_minutes, updated_at)
-            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
+                                      improvement_note, points_earned, session_text, goal_id, task_id,
+                                      is_active, last_update_time, current_elapsed_minutes, updated_at)
+            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
             """;
+        try {
+            executeSaveMerge(sql);
+        } catch (DataIntegrityViolationException e) {
+            if (this.goalId == null && this.taskId == null) {
+                throw e;
+            }
+            // A linked goal/task was deleted while this session was held in
+            // memory (the DB row's FK was SET NULL, but this instance still
+            // carries the stale id). Drop only the dead link and retry rather
+            // than fail — otherwise an active session could never be ended.
+            logger.warn("Session {} link target no longer exists; dropping dead link ({})",
+                    this.id, e.getMessage());
+            if (this.goalId != null && !rowExists("study_goals", this.goalId)) {
+                this.goalId = null;
+            }
+            if (this.taskId != null && !rowExists("tasks", this.taskId)) {
+                this.taskId = null;
+            }
+            executeSaveMerge(sql);
+        }
+
+        logger.debug("Study session saved: {}", this.id);
+    }
+
+    private static boolean rowExists(String table, String id) {
+        Integer count = jdbcTemplate.queryForObject(
+                "SELECT COUNT(*) FROM " + table + " WHERE id = ?", Integer.class, id);
+        return count != null && count > 0;
+    }
+
+    private void executeSaveMerge(String sql) {
         jdbcTemplate.update(sql,
             this.id, this.date, this.startTime, this.endTime,
             this.durationMinutes, this.completed, this.focusLevel,
             this.confidenceLevel, this.notes, this.subject,
             this.topic, this.location, this.outcomeExpected,
             this.actualWork, this.whatHelped, this.whatDistracted,
             this.improvementNote, this.pointsEarned, this.sessionText,
+            this.goalId, this.taskId,
             this.isActive, this.lastUpdateTime, this.currentElapsedMinutes
         );
-
-        logger.debug("Study session saved: {}", this.id);
     }
 
     /**
@@ -303,6 +338,8 @@ private static RowMapper<StudySession> getRowMapper() {
                 rs.getInt("points_earned"),
                 rs.getString("session_text")
             );
+            session.setGoalId(rs.getString("goal_id"));
+            session.setTaskId(rs.getString("task_id"));
             session.setActive(rs.getBoolean("is_active"));
             session.setLastUpdateTime(rs.getObject("last_update_time", LocalDateTime.class));
             session.setCurrentElapsedMinutes(rs.getInt("current_elapsed_minutes"));
@@ -522,6 +559,12 @@ public void setSessionText(String sessionText) {
         this.lastUpdateTime = LocalDateTime.now();
     }
 
+    public String getGoalId() { return goalId; }
+    public void setGoalId(String goalId) { this.goalId = goalId; }
+
+    public String getTaskId() { return taskId; }
+    public void setTaskId(String taskId) { this.taskId = taskId; }
+
     public boolean isActive() { return isActive; }
     public void setActive(boolean isActive) { this.isActive = isActive; }
 

src/main/java/com/studysync/domain/service/StudyService.java

@@ -360,7 +360,20 @@ public boolean deleteStudyGoal(String goalId) {
     }
 
     public StudySession startStudySession() {
+        return startStudySession(null, null);
+    }
+
+    /**
+     * Starts a study session optionally linked to a goal and/or task (issue #17).
+     *
+     * @param goalId optional ID of the study goal this session works on
+     * @param taskId optional ID of the task this session works on
+     * @return the started session
+     */
+    public StudySession startStudySession(String goalId, String taskId) {
         StudySession session = new StudySession();
+        session.setGoalId(goalId);
+        session.setTaskId(taskId);
         session.startSession();
         session.save();
         markDirtyAndSaveLocally("study session start");

src/main/java/com/studysync/presentation/ui/components/CalendarViewPanel.java

@@ -1284,8 +1284,30 @@ private void showAddGoalDialog(LocalDate date) {
         goalTextArea.setPromptText("e.g., Complete Chapter 5, Practice 10 problems, Review notes from class...");
         goalTextArea.setPrefRowCount(3);
         goalTextArea.setWrapText(true);
-
-        content.getChildren().addAll(instructionLabel, goalTextArea);
+
+        Label taskLabel = new Label("Link to task (optional):");
+        TaskStyleUtils.fontBold(taskLabel, 12);
+        ComboBox<Task> taskCombo = new ComboBox<>();
+        taskCombo.setPromptText("None");
+        taskCombo.setMaxWidth(Double.MAX_VALUE);
+        taskCombo.getItems().add(null);
+        taskCombo.getItems().addAll(taskService.getActiveTasks());
+        taskCombo.setCellFactory(lv -> new ListCell<>() {
+            @Override
+            protected void updateItem(Task item, boolean empty) {
+                super.updateItem(item, empty);
+                setText(empty || item == null ? "None" : item.getTitle());
+            }
+        });
+        taskCombo.setButtonCell(new ListCell<>() {
+            @Override
+            protected void updateItem(Task item, boolean empty) {
+                super.updateItem(item, empty);
+                setText(empty || item == null ? "None" : item.getTitle());
+            }
+        });
+
+        content.getChildren().addAll(instructionLabel, goalTextArea, taskLabel, taskCombo);
         dialogPane.setContent(content);
 
         // Enable/disable OK button based on input
@@ -1305,7 +1327,9 @@ private void showAddGoalDialog(LocalDate date) {
         dialog.showAndWait().ifPresent(goalDescription -> {
             if (!goalDescription.isEmpty()) {
                 try {
-                    studyService.addStudyGoal(goalDescription, date);
+                    Task linkedTask = taskCombo.getValue();
+                    studyService.addStudyGoal(goalDescription, date,
+                            linkedTask != null ? linkedTask.getId() : null);
                     updateCalendarDisplay();
 
                     // Show confirmation

src/main/java/com/studysync/presentation/ui/components/StudyPlannerPanel.java

@@ -294,8 +294,32 @@ private void createSessionSection(VBox mainContent) {
         sessionStatusLabel = new Label("No active session");
         TaskStyleUtils.fontNormal(sessionStatusLabel, 14);
 
+        // Optional goal/task link for the session (issue #17)
+        ComboBox<Object> linkCombo = new ComboBox<>();
+        linkCombo.setPromptText("Link to (optional)");
+        linkCombo.setCellFactory(lv -> sessionLinkCell());
+        linkCombo.setButtonCell(sessionLinkCell());
+        linkCombo.setOnShowing(e -> populateSessionLinkCombo(linkCombo));
+
         startSessionBtn.setOnAction(e -> {
-            currentSession = studyService.startStudySession();
+            // Re-validate the selection against the DB: the goal/task may have
+            // been deleted since the combo was populated, and a stale id would
+            // violate the session's FK. Fall back to an unlinked session.
+            Object link = linkCombo.getValue();
+            String goalId = null;
+            String taskId = null;
+            if (link instanceof StudyGoal goal) {
+                goalId = StudyGoal.findById(goal.getId()).map(StudyGoal::getId).orElse(null);
+                String linkedTaskId = goal.getTaskId();
+                if (goalId != null && linkedTaskId != null && !linkedTaskId.isBlank()
+                        && Task.findById(linkedTaskId).isPresent()) {
+                    taskId = linkedTaskId;
+                }
+            } else if (link instanceof Task task) {
+                taskId = Task.findById(task.getId()).map(Task::getId).orElse(null);
+            }
+            currentSession = studyService.startStudySession(goalId, taskId);
+            linkCombo.setValue(null);
             sessionTextArea.clear();
             startSessionTimer();
             syncSessionControls();
@@ -309,7 +333,7 @@ private void createSessionSection(VBox mainContent) {
             }
         });
 
-        sessionControls.getChildren().addAll(startSessionBtn, endSessionBtn, sessionStatusLabel);
+        sessionControls.getChildren().addAll(startSessionBtn, linkCombo, endSessionBtn, sessionStatusLabel);
 
         sessionTextArea = new TextArea();
         sessionTextArea.setPromptText("Write your session notes, thoughts, or study content here…");
@@ -847,16 +871,18 @@ private void populateGoalsPanel(VBox goalsPanel, Task task) {
                 Label noGoals = new Label("No goals linked to this task for this date.");
                 TaskStyleUtils.fontNormal(noGoals, 12);
                 noGoals.setTextFill(Color.web("#7f8c8d"));
-
-                Button addGoalBtn = new Button("+ Create Goal");
-                addGoalBtn.getStyleClass().addAll("btn-purple", "btn-small");
-                addGoalBtn.setOnAction(e -> {
-                    showAddGoalDialog(task);
-                    populateGoalsPanel(goalsPanel, task); // refresh after add
-                });
-
-                goalsPanel.getChildren().addAll(noGoals, addGoalBtn);
+                goalsPanel.getChildren().add(noGoals);
             }
+
+            // A new goal can always be created, even when only missed goals
+            // are waiting for a retry (issue #31).
+            Button addGoalBtn = new Button("+ Create Goal");
+            addGoalBtn.getStyleClass().addAll("btn-purple", "btn-small");
+            addGoalBtn.setOnAction(e -> {
+                showAddGoalDialog(task);
+                populateGoalsPanel(goalsPanel, task); // refresh after add
+            });
+            goalsPanel.getChildren().add(addGoalBtn);
         } else {
             for (StudyGoal goal : activeGoals) {
                 goalsPanel.getChildren().add(buildGoalRow(goal, task));
@@ -1167,9 +1193,91 @@ private VBox buildSessionCard(StudySession session) {
 
         btnRow.getChildren().addAll(detailsBtn, deleteBtn);
         card.getChildren().addAll(timeLabel, durationLabel, focusLabel, pointsLabel, btnRow);
+        Label linkLabel = buildSessionLinkLabel(session);
+        if (linkLabel != null) {
+            card.getChildren().add(card.getChildren().size() - 1, linkLabel);
+        }
         return card;
     }
 
+    /** Renders a goal or task entry in the session link ComboBox. */
+    private ListCell<Object> sessionLinkCell() {
+        return new ListCell<>() {
+            @Override
+            protected void updateItem(Object item, boolean empty) {
+                super.updateItem(item, empty);
+                setText(empty ? null : sessionLinkText(item));
+            }
+        };
+    }
+
+    private String sessionLinkText(Object item) {
+        String text;
+        if (item instanceof StudyGoal goal) {
+            text = "Goal: " + goal.getDescription();
+        } else if (item instanceof Task task) {
+            text = "Task: " + task.getTitle();
+        } else {
+            return "None";
+        }
+        return text.length() > 60 ? text.substring(0, 57) + "\u2026" : text;
+    }
+
+    /** Fills the link ComboBox with today's goals, then tasks not already covered by one. */
+    private void populateSessionLinkCombo(ComboBox<Object> combo) {
+        Object selected = combo.getValue();
+        combo.getItems().clear();
+        combo.getItems().add(null);
+        LocalDate today = dateTimeService.getCurrentDate();
+        List<StudyGoal> goals = studyService.getStudyGoalsForDate(today).stream()
+                .filter(g -> !g.isAchieved())
+                .toList();
+        combo.getItems().addAll(goals);
+        Set<String> linkedTaskIds = goals.stream()
+                .map(StudyGoal::getTaskId)
+                .filter(id -> id != null && !id.isBlank())
+                .collect(java.util.stream.Collectors.toSet());
+        taskService.getTasksForDate(today).stream()
+                .filter(t -> !linkedTaskIds.contains(t.getId()))
+                .forEach(combo.getItems()::add);
+        // Re-select by id: StudyGoal has no equals(), and the previously
+        // selected instance is never in the freshly loaded list.
+        combo.setValue(combo.getItems().stream()
+                .filter(item -> sameLinkTarget(item, selected))
+                .findFirst().orElse(null));
+    }
+
+    private static boolean sameLinkTarget(Object item, Object selected) {
+        if (item instanceof StudyGoal goal && selected instanceof StudyGoal prev) {
+            return goal.getId().equals(prev.getId());
+        }
+        if (item instanceof Task task && selected instanceof Task prev) {
+            return task.getId().equals(prev.getId());
+        }
+        return false;
+    }
+
+    /** Small muted label describing the session's goal/task link, or null when unlinked. */
+    private Label buildSessionLinkLabel(StudySession session) {
+        String text = null;
+        if (session.getGoalId() != null) {
+            text = StudyGoal.findById(session.getGoalId())
+                    .map(g -> "Goal: " + g.getDescription()).orElse(null);
+        }
+        if (text == null && session.getTaskId() != null) {
+            text = Task.findById(session.getTaskId())
+                    .map(t -> "Task: " + t.getTitle()).orElse(null);
+        }
+        if (text == null) {
+            return null;
+        }
+        Label link = new Label(text.length() > 40 ? text.substring(0, 37) + "\u2026" : text);
+        link.setGraphic(TaskStyleUtils.iconLabel("\u29BF", 10));
+        TaskStyleUtils.fontNormal(link, 11);
+        link.setTextFill(Color.web("#7f8c8d"));
+        return link;
+    }
+
     private VBox buildIncompleteSessionCard(StudySession session) {
         VBox card = new VBox(5);
         card.setPadding(new Insets(10, 12, 10, 12));
@@ -1231,6 +1339,10 @@ private VBox buildIncompleteSessionCard(StudySession session) {
         btnRow.setAlignment(Pos.CENTER_RIGHT);
 
         card.getChildren().addAll(statusLabel, timeLabel, durationLabel, btnRow);
+        Label linkLabel = buildSessionLinkLabel(session);
+        if (linkLabel != null) {
+            card.getChildren().add(card.getChildren().size() - 1, linkLabel);
+        }
         return card;
     }
 

src/main/resources/schema.sql

@@ -63,11 +63,15 @@ CREATE TABLE IF NOT EXISTS study_sessions (
     improvement_note TEXT,
     points_earned INTEGER DEFAULT 0,
     session_text TEXT,
+    goal_id VARCHAR(50),
+    task_id VARCHAR(50),
     is_active BOOLEAN DEFAULT FALSE,
     last_update_time TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     current_elapsed_minutes INTEGER DEFAULT 0,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+    -- goal_id/task_id FKs are added in the migrations section below, after
+    -- the study_goals table exists.
 );
 
 -- ===================================
@@ -207,6 +211,15 @@ ALTER TABLE study_goals ADD COLUMN IF NOT EXISTS replanned_for_date DATE;
 -- but excluded from active planner views.
 ALTER TABLE study_goals ADD COLUMN IF NOT EXISTS failed BOOLEAN DEFAULT FALSE;
 
+-- Link study sessions to an optional goal/task (issue #17). Named constraints
+-- keep the ALTERs idempotent for both fresh and migrated databases.
+ALTER TABLE study_sessions ADD COLUMN IF NOT EXISTS goal_id VARCHAR(50);
+ALTER TABLE study_sessions ADD COLUMN IF NOT EXISTS task_id VARCHAR(50);
+ALTER TABLE study_sessions ADD CONSTRAINT IF NOT EXISTS fk_study_sessions_goal
+    FOREIGN KEY (goal_id) REFERENCES study_goals(id) ON DELETE SET NULL;
+ALTER TABLE study_sessions ADD CONSTRAINT IF NOT EXISTS fk_study_sessions_task
+    FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE SET NULL;
+
 -- Add per-attempt goal lifecycle columns. Legacy columns remain intentionally:
 -- schema.sql is re-run on every startup, so destructive DROP COLUMN migrations
 -- would make the compatibility backfill below unsafe on later launches.